Proper cleaning of engine bay - old dirt and grease


Active Member
Oct 26, 2018
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Parker, CO
So I have years worth of dirt and grease caked in my engine bay in various places. I've tried the sprays and doing things by hand and it's certainly helped but I'm just plain in need of a professional. Any suggestions of what process or place to get it all off? I've tried calling rental places for a heavy duty steam machine but they only have heated water sprayers. Seems like I'd need something machine related for getting in nooks and crannies with thick grease build up, not a "done by hand" job. Any suggestions?
You can't rent gasoline powered steam pressure washers at many tool & equipment rental stores. They are very hefty.
Your best bet is to find someone that will steam clean the engine compartment etc. Try a truck & bus repair shop and keep searching for one to rent.
If you have a local car wash with a hand wand sprayer, soak the areas with a good degreaser (Super Clean, Gunk Foaming Degreaser etc.) Then drive to the car wash. Make sure you cover and protect the electronics and any painted surfaces that you don't want damaged and use the high pressure wash cycle. Again, make sure everything is protected!!!! I've done this and it saves a mess at home and cleans very well. The key is to ensure the degreaser penetrates the greasy areas. It helps to scrape the worst gunk off first, which it sounds like you've done that.
Before and after...


I personally like diesel fuel in a squirt bottle and a stiff round brush. Big tray with a lip under the car. Then anything I am going to repaint hit it with brake cleaner.

And a bunch of blue paper towels.
Years ago, in an article on car cleaning, the best type of cleaner was a steam cleaner. BUT there were cautions to have somebody do it that knew what to NOT steam clean. Things like bearings which could be de-lubed by the steam, or similar. End result, a poor operator could do more damage than not, they noted, yet everything would be spotless when they were done.

If most of the deposits you're trying to remove are (or were, before they dried out) oil based, then putting an oil-based solution on them first, to soften them back up before you try to wash them off, is best. Why the diesel and Varsol solvent tend to work as good as they do. Like using car wax to soften "road tar" to remove it by first liquifying it somewhat.

Other than the truck/bus repair/wash shops, you might consider "graffiti removal" operations, who use a pressure washer situation. Which also means they are "portable" and come to where you are.

Only thing is that if you're looking to clean "every nook and crannie", then you'll probably end up removing some surface coatings/sealers in the process too. Which will have to be replaced somehow or another.

Just some thoughts,
Look up mobile pressure washer. These guys roll out to you and do buses big Motorhomes and tractor trailers. A good one will have a water softener on his trailer so they can wash off your car w a spotless rinse. Beware of I can wash the whole car for you ( they sometimes use mop and glow type wax in the water ) too. Spot free rinse is all you’ll need. Usually cheaper and faster than renting.
Easy-off and the local car wash. Just watch the aluminum and painted surfaces, but it will get through the grease.
I go with steam when I'm ready to detail out the engine compartment. Just run it up to my local detail shop. Steam cleaning the engine bay and carpets are worth the price and end results are far superior to what I could do at home.
These two points really set a car off when I'm selling a vehicle.
Ya gotta clean before you paint anything. Purple power works great on heavy grease, followed by Dawn dishwasher liquid in a spray bottle.
Apply it to a cold surface and drive to a spray wash, (as suggested above), Power and steam washers are to powerful and can cause damage to wiring, plastic etc.
This will require two separate procedures as both need to be applied to a cold surface. I usually just let the engine run while spraying.
Protect your painted/polished surfaces.
I like to use simple green. Blast the areas first with a decent pressure washer to get most of the accumulated grease and dirt off, then wait for the car to dry. Then spray it down with simple green and let it sit for about 10 min or so, then pressure wash it again. Nice thing with simple green is it won't hurt your will strip off wax and polish but won't hurt single stage paints or clear coats.